Polyesterimides from dicyano diamide-hydrazine reaction products

ABSTRACT

A PROCESS FOR THE PRODUCTION OF POLYESTER RESINS CONTAINING 5-MEMBERED IMIDE RINGS FORMED WHEN HEATED TO TEMPERATURES ABOVE 250*C. FROM POLYHYDRIC ALCOHOLS, POLYVALENT AROMATIC CARBOXYLIC ACIDS AND POLYVALENT AMINO COMPOUNDS, OPTIONALLY IN ADMIXTURE WITH OTHER ALIPHATIC AND/OR AROMATIC POLYVALENT CARBOXYLIC ACIDS, OR FROM REACTIVE DERIVATIVES OF THESE COMPOUNDS. A PORTION OF THE POLYVALENT AMINO COMPOUNDS IS THE REACTION PRODUCT OF DICYANO DIAMIDE WITH HYDRAZINE.

United States Patent Office US. Cl. 260-75 N 8 Claims ABSTRACT OF THE DISCLOSURE A process for the production of polyester resins containing S-membered imide rings formed when heated to temperatures above 250 C. from polyhydric alcohols, polyvalent aromatic carboxylic acids and polyvalent amino compounds, optionally in admixture with other aliphatic and/or aromatic polyvalent carboxylic acids, or from reactive derivatives of these compounds. A portion of the polyvalent amino compounds is the reaction product of dicyano diamide with hydrazine.

This invention relates to a process for the production of polyester resins containing S-mernbered imide rings, to their use in the production of stoving insulation and to a process for the production of insulating coatings on electric conductors.

Processes for the production of polyester imide resins suitable for lacquering electric conductors are already known cf. British patent specifications 937,377; 1,082,- 181; 1,067,541; 1,067,542 and 1,127,214; Belgian patent specification 663,429; French patent specification 1,391,- 834; East German patent specification 30,838; German Offenlegungsschriften 1,494,454 and 1,494,413.

After they have been baked or stoved on to copper wire, lacquer films of conventional polyester imide resins show outstanding thermal stability, excellent elasticity, a high resistance to solvents and satisfactory behaviour in heat-shock tests. The pencil hardness of these lacquer films usually amounts to between 3 and 4H and can only be increased at the expense of an appreciable loss of elasticity. However, pencil hardnesses in excess of 5H are desirable because the requirements which the surfaces of enamelled wires have to satisfy in view of modern winding processes of the kind use in the manufacture of motors and rotors, have risen very considerably.

The object of the present invention is to produce new polyester resins containing imide groups which, after stoving on to electric conductors, give coatings of improved hardness.

Surprisingly, it has now been found that this object can be achieved without in any way affecting the other excellent properties of conventional resins, providing reaction products of dicyano diamide with hydrazine prepared at temperatures between room temperature and around 280 C. are condensed into the polyester resin. Accordingly, the present invention relates to a process for the production of polyesters which contain S-membered imide rings and/ or which form S-membered imide rings when heated to temperatures above 250 C. from polyhydric alcohols, polyvalent aromatic carboxylic acids containing at least 2 carboxyl groups in the ortho-position and at least one other functional group, and polyvalent amino compounds optionally in admixture with other aliphatic and/or aromatic polyvalent carboxylic acids, or from reactive derivatives of these compounds, which process is distinguished by the fact that from 5 to 100 mol Patented Dec. 21, 1971 percent of the polyvalent amino compounds used as starting product, based on the total quantity of polyvalent amino compounds, consist of reaction products of dicyano diamide with hydrazine prepared at temperatures between room temperature and about 280 C.

Thus, the polyester resins containing S-membered imide rings prepared by the process according to the invention differ from conventional polyester resins containing imide rings in that they contain the aforementioned reaction products of dicyano diamide with hydrazine condensed into them as a new component. The remaining components or starting products condensed into the resins may be the same as in conventional polyester resins containing imide groups. Reference is made in this connection to the patent specifications quoted earlier on. For this reason, there is no need to provide a comprehensive list of the various possible reaction components.

Preferred starting materials for the process according to the invention include reaction products of dicyanodiamide with hydrazine that have been prepared at temperatures of from about 30 to about C. Reaction product-s of this kind are preferably condensed in quantities of from about 10 to 50 mol percent, based on the total quantity of polyvalent amino compounds and reaction products of dicyano diamide with hydrazine. In addition, it is preferred to prepare these reaction products by reacting dicyano diamide and hydrazine in a molar ratio of from 0.811 and 1:5, preferably in a molar ratio of 1:1 to 1:1.8, advantageously in an organic solvent miscible with hydrazine and/or water at the temperatures indicated above. It is possible in this way to obtain a solution which may be used either as such, i.e. without any need to isolate the reaction products before hand, for the preparation of the polyester resin according to the invention. It is of particular advantage to use a solvent which does not interfere in any way with the reaction with the other starting components and which does not have to be removed. Accordingly, it is preferred to use as solvents for the reaction between dicyano diamide and hydrazine for example polyhydric alcohols which can in any case be used as further reaction components.

There is no need for the reaction product of dicyano diamide with hydrazine to be an individual chemically specific compound. On the contrary, this reaction product is usually a mixture of several compounds, although this mixture can be used in accordance with the invention. Providing dicyano diamide and hydrazine are used in suitable quantities and the reaction conditions applied are suitably selected, it is possible preferentially to obtain 3,5-diamino- 1,2,4-triazole (US. Patent specification 2,648,671) as reaction product. In addition, the pyroguanazole obtained at elevated temperature from dicyano diamide and hydrazine (K. A. Hoffman and O. Ehrhardt, Berichte der Deutschen Chemischen Gesellschaft 45/12 (1912), pages 2731-2740) may also be used.

According to the prior art, trimellitic acid and/or its anhydride is preferably used as the carboxylic acid containing at least two carboxyl groups in the ortho-position and at least one other functional group. This acid or its anhydride is also preferably used in the process according to the invention. The process according to the invention may be carried out by reacting the polyvalent carboxylic acid containing at least two carboxyl groups in the ortho-position and at least one other functional group first with the reaction product of dicyano diamide and hydrazine to form bis-3,5-(carboxylic acid amido)-l,2,4- triazole and/or bis-3,5-(carboxylic acid imido)-l,2,4-triazole and then with the other starting materials. The aforementioned triazoles formed as intermediate products may be reacted after isolation and purification or directly in the form of the reaction solutions with the other start ing components to form the polyester resins according to the invention. If as already mentioned trimellitic acid or a derivative thereof (anhydride and/or ester) is used as the carboxylic acid, bis-3,5-(trimellitic acid imido)-1,2,4-

triazole and/or bis-3,5-(trimellitic acid amido) 1,2,4- triazole are formed as intermediate products in the reaction with 3,5-diamino-1,2,4-triazole. These compounds are crystallised substances which can readily be isolated in highly pure form without any need for special purification stages.

The present invention also relates to the use of the polyester resins defined above in the production of stoving insulations on electric conductors and to a process for the production of insulating coatings on electric conductors by coating the conductors with a thermosetting lacquer solution and heating the conductors thus coated to elevated temperature, which process is distinguished by the fact that the lacquer solution contains polyester resins prepared in accordance with the above definition. Production of the polyester resins and/or production of the insulating coatings by stoving at elevated temperatures may be carried out in known manner optionally in the presence of conventional catalysts and/or other auxiliaries. There is no need to provide a detailed list here either because catalysts and/or auxiliaries of this kind are discussed at length in the patent specifications quoted earlier on. The polyester resins prepared in accordance with the present invention may also be mixed with other resins in order thus to obtain stoving insulations on electric conductors with mixtures of this kind or their solutions.

The insulating coatings on electric conductors produced by the process according to the invention show the outstanding properties of conventional polyester imide resins, but a much greater hardness of from 7 to 8H which hitherto had been considered impossible. This is an extremely surprising technical effect which hitherto it has been impossible to achieve with highly heat resistant insulating coatings.

The invention is illustrated by the following examples. Examples 1 to 7 illustrate the production of the polyester resins in accordance with the invention.

EXAMPLE 1 97.0 g. (0.5 mol) of dimethylterephthalate, 348.0 g. (1.3 mols) of tris(2-hydroxyethyl)-isocyanurate, 186.0 g. (3 mols) of ethylene glycol are introduced together with 30 g. of commercial cresol into a three-necked flask equipped with stirring mechanism, thermometer and column. Following the addition of 1 g. of butyl titanate, the contents of the flask are heated in a nitrogen atmosphere. Distillation of the methanol liberated by transesterification begins at around 140 to 150 C. 32 g. of methanol have been distilled off after some 3 hours when the temperature amounts to 220 C.

After cooling to around 170 C., 288 g. (1.5 mols) of trimellitic acid anhydride and 149 g. (0.75 mol) of 4,4- diamino diphenylmethane are added and condensed in by heating to ZOO-220 C. until 54 g. of water have been distilled off.

After cooling to around 170 C., 288 g. (1.5 mols) of trimellitic acid anhydride and 74.2 g. (0.75 mol) of 3,5- diamino-1,2,4-triazole are added and condensed at 200- 220 C. until another 54 g. of water have been distilled off.

Ethylene glycol is then distilled off in vacuo at 200 C. until the viscosity of the resin as measured on a 30% solution in m-cresol at 25 C., amounts to 1012 op. The resin is then diluted with commercial cresol into a 50% solution.

EXAMPLE 2 349 g. (1.8 mols) of dimethyl terephthalate, 120 g. (1.3 mols) of glycerine,

124 g. (2 mols) of glycerine,

124 g. (2 mols) of ethylene glycol and 100 g. of cresol are transesterified with 1.0 g. of zinc acetate at a temperature of up to 220 C. in a three-necked flask equipped with stirring mechanism, thermometer and rectification column. 116 g. of methanol are distilled off.

After cooling to around 170 C.

192.0 g. (1 mol) of trimellitic acid anhydride, 99.0 g. (0.5 mol) of 4,4-diamino diphenylmethane, and 19.8 g. (0.2 mol) of 3,5-diamino-1,2,4-triaz0le are added. 36 g. of water are distilled off by continued heating up to 220 C.

Another 192.0 g. (1 mol) of trimellitic acid anhydride, 99.0 g. (0.5 mol) of 4,4-diamino diphenylmethane, and 19.8 g. (0.2 mol) of 3,5-diamino-1,2,4-triazole are added to the melt cooled to around 170 C. After another 36 g. of Water have been distilled off, glycol is distilled off by increasing the temperature to 240 C. until the resin has a viscosity of 1830 cp. as measured on a 33.3% solution in m-cresol at 25 C. The resin is dissolved in commercial cresol to form a 50% solution.

EXAMPLE 3 A resin is condensed as described in Example 2, except that the two portions each of 19.8 g. of 3,5-diamino-1,2,4- triazole were each replaced by 66 g. of a solution obtained as follows:

420 g. (5 mols) of dicyanodiamide 900 g. of ethylene glycol 500 g. of water and 340 g. (5.5 mols) of hydrazine hydrate EXAMPLE 4 230 g. (1.2 mols) of trimellitic acid, anhydride,

99 g. (0.5 mol) of 4,4'-diamino diphenylmethane,

9.9 g. (0.1 mol) of 3,S-diamino-1,2,4-triazole,

35 g. (0.56 mol) of ethylene glycol,

65 g. (0.25 mol) of tris-(2-hydroxyethyl)-isocyanurate 300 g. of cresol are heated with 1 g. of zinc acetate in a three-necked flask equipped with stirring mechanism, thermometer and rectification column. The heating rate is regulated in such a Way that the temperature at the head of the column does not exceed 102 C. After 7 hours, the temperature of the flask is 184 C., the product has become clear, and 45 ml. of water and a little cresol are distilled off.

After another 4 hours heating to 200 C., the contents of the flask are diluted with g. of cresol to form an approximately 50% resin solution.

EXAMPLE 5 97.0 g. (0.5 mol) of dimethyl terephthalate, 348.0 g. (1.3 mols) of tris-(2-hydroxyethyl)isocyanurate 186.0 g. (3.0 mols) of ethylene glycol are transesterified in the same way as described in Example 1.

After cooling to around C.,

288 g. (1.5 mols) of trimellitic acid anhydride and 149 g. (0.75 mol) of 4,4'-diamino diphenylmethane are added, and the reaction mixture is heated until 54 g. of water have been distilled off,

After cooling to 170 C.

288 g. (1.5 mols) of trimellitic acid anhydride,

129 g. (0.65 mol) of 4,4-diamino diphenylmethane and 9.9 g. (0.1 mol) of 3,5-diamino-1,2,4-triazole are added and the mixture heated until another 54 g. of

reaction, producing an increase in the temperature of the solution to around 5 60 C. The reaction mixture is stirred for 3 hours at that temperature. The resulting solution thus contains a reaction product of dicyano diamide Water have been distilled ofi. Some of the ethylene glycol 5 and hydrazine. Following the addition of 384 g. of triis distilled off in vacuo at 200 C. The resin has a viscosity mellitic acid anhydride to this solution, the solution is of 1050 cp. as measured on a 30% solution in m-cresol at brought to the 'boil. After 8 hours boiling under reflux, the 25 C, yellow deposit precipitated is filtered off .and washed with The resin is diluted with commercial cresol to form a a little water. After drying 'at 80 C. in a vacuum drying 50 1% resin l i 10 cabinet, 440 g. (around 91% of the theoretical) of bis-3,5

(trimellitic acid-1-amido)-1,2,4-triazole with an acid num- EXAMPLE 6 ber of 460 mg. KOH/ g. are obtained. 484 g. of this com 97 g. (0.5 mol) of dimethyl terephthalate, pound which may also be used as a starting material in 4 (13 mols) f tris (g hydroxyethyl)qsocyanurate, the process accord ng to the 1I1V6l'1t1011, are heated for 8 186 (33111015) f ethylene glycol 15 hours 180 m a vacuudrn dryf1ng calbirtigt. Thle correspon mg 1m1 o compoun 1s orme roug ring are transestenfied m the Same Way as described m closure. Bis-3,5-(trimellitic acid imido)-1,2,4-triazole with ample 0 an acid number of 250.5 is obtained in a yield of 445 g.

After cooling to around 170 C., (99% of the theoretical yield) 288 g. (1.5 mols) of trimellitic acid anhydride and 149 g. (0.75 mol) of 4,4'-diamino diphenylmethane Comparison Test 1 Following the prior art, a resin is prepared as described 35: 2:3 z g fgfi ffiffi gg heated untll 54 of in Example 5, except that the 3,5-diamir1o-1,2,4-triazole After Cooling to 6 used 1n Example 1s replaced by an equimolar quantity 288 g. (1.5 mols) of trimellitic acid anhydride, of dlptienylmethane' A 50% resm 77 g. (0.39 mol) of 4,4'-diamino diphenylmethane and Solution m cqmmerclal cresol 1S Prepared 59 (024 mol) of pyroguanazole The followlngExample 8 descr bes the use of the polyesters prepared in accordance with Examples 1 to 7 1n (prepared in accordance with K. A. Hoffman and O. the production of stoving insulations and the process for Erhardt, Berichte der Deutschen Chemischen Gesellthe production of insulating coatings on electric schaft 45/ 12 (1912) pages 27312740) are added and the conductors. mixture heated until another 54 g. of water have been EXAMPLE 8 distilled Lacquers of the following composition are prepared k gg g g gg f ig g i i g g ig from the resinsolutions in accordance with Examples 1 to amp 0 1 1 m 7 and comparison test 1: prepared. Parts EXAMPLE 7 50% resinsolutions in cresol 60.00 194 g. (1.0 mol) of dimethyl terephthalate, Commercial cresol 15.00 348 g. (1.3 mols) of tris-(Z-hydroxyethyl)-isocyanurate 40 Solvent naphtha 15.00 186 g. (3.0 mols) of ethylene glycol Polymeric butyl titanate 0.30 are transesterified in the same way as described in Exam- Xylene ple 1 until 64 g. of methanol have been distilled ofi. 100 00 After cooling to around 170 C., Th 1 1 d 6 l 8 a ese acquers are app ie in ayers to a 0. mm. S zi g; aim L3; bls (tnmenmc acid lmldo) d1 diameter copper wire by means of roller and felt in a 112 g of bis 3s (trimenitic acid imido) 12, horlzontal wire-lacquering ozlen 3 metres long at a tem- Hriazole perature of from 410 to 450 C., and then hardened. The WlI'e 1s lacquered at a rate of 9 to 13 metres per minute. are added and the mixture heated until 36 g. of water Testing of the lacquered wires produced the results set have been distilled off. out in Table 1.

TABLE 1 Lacquer prepared from the resin according to Example- Comparison 1 2 3 4 5 6 7 Test 1 Pencil hardness 8H 8H 8H 7H 6H 8H 8H 4H Pencil hardness after 30 minutes storage in ethanol at 0 8H 8H 8H 7H 6H 7-8H 8H 4H Heat shock test 30 mins. at 200 C S S S S S S S S 30 mlns. at 250 C S Cracks S S S S S Winding strength when wire is wound around its own diameters after pre-elongatlon (percent). 20 15 15 25 25 20 25 NOTE: S=Satisfactory.

We claim:

1. In a polyester resin comprising the condensation product of an aromatic polycarboxylic acid having at least 2 carboxyl groups in the ortho-position and at least one other functional group; a polyhydric alcohol; and a polyamino compound, the improvement which comprises from about 5 to about 100 mol percent of the total amount of polyamino reactants being a reaction product of dicyano diamide with hydrazine in a molar ratio of from about 0.8:1 to about 1:5, said reaction product being prepared at temperatures up to about 280 C.

2. A polyester resin as claimed in claim 1, further comprising a second aromatic polycarboxylic acid, an

carefully heated. At around 30 C. there is an exothermic aliphatic polycarboxylic acid or mixtures thereof.

3. A polyester resin as claimed in claim 1, wherein the reaction product of dicyano diamide and hydrazine is present in an amount of from 10 to 50 mol percent, based on the total amount of polyamino reactants.

4. A polyester resin as claimed in claim 1, wherein the reaction product of dicyano diamide with hydrazine is prepared at temperatures between 20 and 130 C.

5. A polyester resin as claimed in claim 1, wherein the dicyano diamide and the hydrazine are reacted in a molar ratio of from about 1:1 to about 1:1.8.

6. A polyester resin as claimed in claim 1, wherein the reaction product is 3,5-diamino-1,2,4-triazole.

7. A polyester resin as claimed in claim 1, wherein the reaction product is pyroguanazole.

8. A polyester resin as claimed in claim 1, wherein the polycarboxylic acid is a member selected from the group consisting of trimellitic acid, trimellitic acid anhydride and mixtures thereof.

References Cited UNITED STATES PATENTS MELVIN GOLDSTEIN, Primary Examiner US. Cl. X.R.

1l7l28.4; 260-33.4 P 

